Protective coating of uranium and thorium



United States Patent PROTECTIVE COATING OF URANIUM AND THORIUM Roger J. A. Potvin, Quebec, Quebec, Maurice J. Lavigne, Deep River, Ontario, and Jacques J. E. Laberge, St. Jean, Quebec, Canada, assignors to Atomic Energy of Canada Limited, Ottawa, Ontario, Canada No Drawing. Application November 2S, 1955 Serial No. 549,554

Claims priority, application Canada November 30, 1954 2 Claims. (Cl. 117-130) This invention relates to the protective coating of uranium, thorium and alloys of either of them.

The object of the invention is to provide an effective method for the application of a uniformly adherent coating which will protect these metals from corrosion and at the same time provide a base for subsequent nonmetallic coatings or for the electrolytic deposition of other metals. Because of its great afiinity for oxygen and other gases, as well as its relatively high position in the electrochemical series of metals, uranium is particnlarly diflicult to successfully coat with other metals.

It has been found that the deposition of a thin film of arsenic on the surface of such metals renders them noncorrosive and receptive to further coatings as desired. The film may be deposited by dipping in an aqueous solution of arsenic acid or its salts or it may be applied electrolytically.

In carrying out the invention such metal is subjected to a normal preliminary mechanical polishing or other treatment to remove dirt and any surface coating. It is then immersed in an aqueous solution of arsenic acid or a salt thereof. An aqueous solution of 0.1 to 11.5% of arsenious oxide has been found most satisfactory. The bath solution is heated and the metal is immersed in it to receive the desired coating. The bath may be heated to its boiling point but lower temperatures are Patented Dec. 1, 1959 effective. The time of immersion to obtain a good coating may vary from 1 to 15 minutes or more depending upon the temperature employed and the concentration of the solution. and concentrations longer time is required to provide a good coating. For example With a concentration of 0.1% and a temperature of 80 C. the time of immersion is about 30 minutes, whereas immersion for one to two minutes in the more concentrated solution provides the desired coating.

Passage of an electric current through the bath in which the metal is immersed decreases the time required.

The deposit consists of a film of arsenic approximately A. to a few 100,000ths of an inch thick and has been found to be highly resistant to corrosion under rigorous conditions.

The surface thus formed on these metals is well adapted for further electrolytic coating but the electrolyte should be free from complex salts, such as cyanide, which tend to destroy the arsenic film. An electrolyte containing the metal to be deposited in the form of a sulphate, perchlorate or acetate was most satisfactory.

The arsenic coating may be polished and buffed without disruption and enamels and paints may be applied thereto and retained thereon.

What is claimed is:

1. A method of applying an adherent protective coating upon the surface of one of a group consisting of uranium, thorium and their alloys which comprises immersing the metal having a clean surface in an aqueous solution consisting essentially of 0.1 to 11.5% of arsenious oxide to cause arsenic to deposit on the surface of the metal.

2. The method defined in claim 1 wherein the solution during immersion is heated to a temperature not exceeding its boiling point.

UNITED STATES PATENTS Glover et al May 18, 1948 At the lower temperatures Gravell May 21, 1929 

1. A METHOD OF APPLYING AN ADHERENT PROTECTIVE COATING UPON THE SURFACE OF ONE OF A GROUP CONSISTING OF URANIUM, THORIUM AND THEIR ALLOYS WHICH COMPRISES IMMERSING THE METAL HAVING A CLEAN SURFACE IN AN AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF 0.1 TO 11.5% OF ARSENIOUS OXIDE TO CAUSE ARSENIC TO DEPOSIT ON THE SURFACE OF THE METAL. 